Implantable cardiac defibrillators (ICDs) perform two main functions: detecting fibrillation and delivering defibrillation shocks. A variety of issues are associated with use of ICDs. Some issues pertain to the patient while others pertain to the ICD. For example, an ICD should extend patient life and even improve quality of life. On the other hand, an ICD should operate efficiently to conserve its limited power supply.
Efficient operation of an ICD involves delivering defibrillation shocks only when required, delivering an initial defibrillation shock that has a high likelihood of success, and delivering defibrillation shocks at energy levels that are not greatly in excess of a minimum required energy level. The first factor depends largely on fibrillation detection algorithms and ICD capabilities related thereto while the second and third operational factors are interrelated.
Many studies have tried to divine “optimal” shock parameters. For example, a study by Inrich “How to program pulse duration or tilt in implantable cardioverter defibrillators”, Pacing Clin Electrophysiol. 2003 January; 26(1 Pt 2): 453-6, presented a system of three related equations in an effort to determine optimal defibrillation shock parameters. While such studies are instructive, a need still exists for better methods to determine or optimize defibrillation shock parameters. Yet further, as described herein, judicious selection of parameters or models or analysis of defibrillation shock information can even yield insight as to cardiac condition.